The invention is primarily applicable for use in a plasma arc torch and it will be described with particular reference thereto; however, the invention has much broader applications and may be used with various torches which are connected to a universal control station or power supply for the purpose of directing power and/or gases to the torch in desired amounts for the purposes of welding, cutting, brazing and other heat related processes. When using plasma for heat processing, a torch is connected to a universal control station which directs the arc current, plasma gas and auxiliary cooling gas, together with electrical current from the universal control station to the torch body or housing. A torch or torch assembly includes the housing on one end, a long flexible cable and a plug on the other end. The cable is employed with the end plug for connecting the torch housing or body onto the control station which includes both the power supply and the supply of gaseous material. The station also contains the microprocessor or other control system for operating the power supply, gas supply and torch itself. Consequently, it is somewhat standard practice to provide the end plug with a specific arrangement of nipples and electrical connectors or terminals for connecting the plug to the stationary universal control station with the gas lines, arc current leads and control conduits all automatically connected in unison.
An operator obtains a torch housing, hose and connector as an assembled unit and manually connects the plug or connector of this assembly onto the power supply or universal control station. The mere connection of the plug to the power supply or control station implements the desired operation of the torch in accordance with the settings of the control station. A unique torch assembly is required for a particular plasma operation. As the operation changes a different torch assembly may be necessary. For this reason, when each connection of the plug to the power supply is made, the operator must adjust the power, gas flow and other desired operating parameters for the specific torch being employed. The operator will thus be assured that the proper settings are made at the power supply.
In a particular facility, many torches having different desired operating parameters are available to be operated by the same universal control station. For this reason, the operator must identify the particular torch being used and be aware of the desired operating parameters to be set for that particular torch. This presents certain disadvantages. The manual setting of the power supply may be erroneous since the operator is often under pressure and is performing the work in a somewhat adverse environment. In addition, the torch selected by the operator for the particular operation may be the incorrect torch. In this situation, the power supply may be adjusted or set for one torch and another torch is actually attached to the power supply. This can be harmful to the equipment. Since plasma torches must be repaired and rebuilt often and replaced by the operator, the need for setting, selecting and otherwise implementing the use of a new torch is extremely common and must be done often by an operator. If the torch is incorrect or the settings are inconsistent with the desired operating parameters for the torch, the torch may not operate efficiently, may not operate at all or may be rapidly deteriorated or be destroyed in a short time. For this reason, facilities establish elaborate systems for identifying torches, coding the torches, documenting desired operating parameters and otherwise assisting the operator in selecting the proper torch and implementing the desired operating parameters for the torch after it has been connected to the power supply or control station. This procedure is costly and, in some respects, is somewhat ineffective since it demands a high level of human input and often results in selection and setting errors.
The present invention overcomes the difficulties in selecting the proper unique torch for a given operation and being assured that the desired operating parameters for the individual plasma torch are set at the power supply or control station used to actuate one of many different torches.
In accordance with the present invention there is provided an improvement in a torch, such as a plasma torch, having specific design features which determine the specific operating characteristics of the torch, wherein the torch has connector means, such as a long flexible cable and plug, for selectively connecting the torch onto a control station for providing electrical power and gas flow to the torch, which electrical power and gas flow are to be matched to the operating parameters of the torch. The improvement in this torch comprises an identification circuit for identifying the torch, wherein the identification circuit has an electrical property unique to the specific characteristics of the torch and means for interrogating the identification circuit to sense the electrical property of the identification circuit. In this manner, the torch itself can be automatically identified by interrogating the identification circuit mounted on the torch. This identification circuit may be located in the torch housing or it may be located in the plug at the end of the flexible cable, which plug connects the torch assembly to the power supply. When the connector, or plug is attached to the universal control station or power supply, the identification circuit in the torch can be interrogated for identifying the torch connected to the power supply. In this manner, the power supply or control station accurately identifies the particular torch connected at its output socket at any given time. In accordance with this concept, the power levels, gas flows and other parameters of the control station can be automatically adjusted by the onboard computer or microprocessor to provide a closed loop system and method wherein the mere connection of a torch will effect an automatic adjustment of the desired operating parameters for optimum operation of the particular torch identified by a circuit carried on the torch. The torch includes both the flexible cable and connector plug, which plug has a pattern of nipples and electrical connects matching a companion socket on the power supply station for the plasma operation.
In accordance with another aspect of the present invention the identification circuit on the torch includes a resistor and the electrical property being interrogated is the approximate resistance of the resistor. This is done, in accordance with the preferred embodiment of the invention, by allowing a voltage of a known value to be applied to a network consisting of a fixed resistor within the control station or power supply and the torch mounted resistor whereby the voltage across the torch mounted resistor is the electrical property of the identification circuit. By selecting a different resistor or resistor network for each of the various torches to be identified, the detected or measured voltage or voltages can be compared and processed to determine the specific identity of the torch connected onto the power supply or control station.
In accordance with one aspect of the invention, the identification circuit is located in the torch housing itself whereas in another aspect of the invention the identification circuit is located in the plug. Since the plug, cable and torch are assembled preparatory to use, both locations of the identification circuit are acceptable. A torch or torch assembly are used interchangeably as only the actual housing or the three components. In the preferred embodiment, the identification circuit is in the torch housing itself since this will assure that the proper torch identification is made without the need for maintenance and manufacturing personnel to make the desired selection by placing the identification circuit in the plug at the end of the flexible cable of the torch assembly. It is appreciated that the torch is broadly defined as including the connector means itself for the purpose of showing that the identification circuit may be located anywhere, as long as it is carried by the torch. The torch can, in this manner, be accurately identified when the plug at the end of the flexible cable is attached to the power supply.
In accordance with another aspect of the preferred embodiment of the invention, the identification circuit is a resistor network including two separate resistors and the electrical property that identifies the torch is the resistance of each of these resistors in a coded combination. In this manner, a first voltage is created that is indicative of the resistance of a first resistor. A second voltage is created which is indicative of the resistance of a second resistor. By using these two separate voltages and separating the voltage range into several distinct levels, the identification code for the plasma torches has two number digits and each number can have several digits. This multiplies the number of torches which can be identified in accordance with the system used in the present invention. To further increase the number of identifiable torches, a third resistor could be used for the purpose of creating a third voltage which could be divided into distinct ranges and would again double the number of torches that could be identified by using the present invention. It has been found that the use of two resistors is preferred and a convenient means for identifying several hundred different specific types of plasma torches.
In accordance with another aspect of the present invention there is provided external means for digitizing the detected resistance of each of the resistors and means for comparing each of the digitized resistances to a two dimensional digital grid having numerical segments assigned to groups of digital coordinates with each of the segments indicative of a particular torch and means for outputting the numerical segment encompassing the detected resistance of the resistors. In this manner, a microprocessor or onboard computer of the control station has a read only memory (ROM) containing a map or table that is a network having A coordinates divided into a selected number of segments, such as 20 and the B coordinates divided into a similar number of numerical segments. In this manner, the map or table is a matrix including 20.times.20 numerical segments, each of which is approximately 9 bits wide and 9 bits long to identify 400 different torches. In this manner, the digitized voltages from reading the various resistors will be within the specific numerical area of a ROM with the various ROM areas assigned to a given torch. Variations in the resistance and in the digitizing of the voltage will not cause misidentification since areas in the ROM are relatively large for each individual torch to be identified. The actual scheme is shown in FIGS. 7 and 8. Other arrangements could be employed for using one or more resistors or other electrical properties to create a voltage which can be digitized, divided into segments or ranges and compared with a numerical pattern to output the identification of a specific, plasma torch.
The present invention also involves a system for automatically identifying a plasma torch having specific design features. The torch has an identification circuit means for identifying the torch, as described above, so that the identification circuit has an electrical property unique to the specific design features of the torch being identified. The torch also has means for interrogating tile identification circuit such as output leads for directing a known current to the identification circuit. The system of the present invention includes means on the control station or power supply for activating the torch interrogation means when the torch is connected to the power supply and means external of the torch for reading the electrical properties of the identification circuit on the torch when the interrogation means of the torch is activated. This system allows for the automatic interrogation and identification of a variety of torches by merely connecting them to the power supply or control station. The system includes the onboard computer for digitizing the voltages indicative of the resistance of the various resistors used in the circuit on the torch and for comparing this digitized resistance to a two dimensional digital grid, such as a read only memory (ROM) map or table having numerical segments assigned to groups of coordinates so that the particular segment or area into which the digitized voltage falls is indicative of a particular torch. Means are also provided for outputting the numerical segment encompassing the selected resistances of the resistors to identify the torch. When the torch is identified, the control station can be adjusted to the proper operating parameters. In the alternative, the control station is adjusted to known operating parameters and the identified torch is rejected if it is not the proper torch.
There is also provided a method for automatically identifying a plasma torch as it is connected to a power supply, which method includes the steps of providing the torch with an identification circuit fixedly associated with the torch for identifying the torch wherein the identification circuit has an electrical property unique to the torch and the step of interrogating the identification circuit to sense the electrical properties so that the torch is identified. This method also includes the steps of comparing the sensed electrical property to a table identifying the specific torches by the electrical property of the identification circuit. This method further includes the concept of setting the desired operating parameters of the power supply by the automatically identified specific torch connected to the power supply and setting the power supply accordingly. In addition, the method can include the additional step of inhibiting the control station or power supply if a sensed property is a preselected value indicating that the torch is wrong or no torch is in place. In this manner, if a torch is connected to the power supply and is not identified or is not a proper torch for a particular power supply setting, the method employs the steps of inhibiting the power supply until proper torch identification has been obtained or a manual override procedure has been performed.
The primary object of the present invention is the provision of an identification system and method for automatically identifying the type of torch connected to a power supply and the improvement in a torch for accomplishing this purpose.
Yet another object of the present invention is the provision of a system, method and improved torch, as defined above, which system, method and improved torch allows for automatic identification of a large number of torches as a torch is connected to a power supply. This object reduces the possibility of an improper torch and/or an improper torch setting for a plasma operation.
Yet another object of the present invention is the provision of a system, method and improved torch, as defined above, which system and method allows for the automatic adjustment of the power supply in the control station of a plasma operation in accordance with the automatic identification of a torch connected to the power supply, so that the proper operating parameters will be used with a given torch.